1. Field of the Invention
This invention relates to the oligomerization of olefins into light, liquid transportation fuels. More specifically, this invention relates to the oligomerization of olefins in a water containing medium.
2. Description of the Prior Art
In the 1930's, gasoline range liquids were produced by reacting olefins. This "polymer gasoline" was made by heating olefins at high temperatures under high pressure. However, due to the exothermic nature of the process these processes were extremely difficult to control. It was not uncommon to have the reaction temperature jump from 800.degree. F. to over 1200.degree. F. in a manner of minutes. The high temperatures and pressures of these processes also left the reaction vessel coated with a powdery coke.
Improvements made to the above process have largely entailed the addition of catalysts. An example of one such process is described in U.S. Pat. No. 2,422,692 which discloses a process for producing isobutane and other liquid hydrocarbons from propylene and other gaseous olefins. This reaction is carried out over a polarizing catalyst at a temperature of from 200.degree. C. to 500.degree. C. and at a pressure of from 100 psi to 1000 psi.
The instant invention pertains to dense, water containing fluids at elevated temperatures and pressures. In part, the instant invention pertains to the use of supercritical fluids. A fluid which is at both a temperature and pressure exceeding its critical temperature and pressure is a supercritical fluid. A supercritical fluid exists as a form of matter in which its liquid and gaseous states are indistinguishable from one another. The critical temperature of a fluid is the temperature above which that fluid cannot be liquified by an increase in pressure. The critical pressure of a fluid is simply the pressure of the fluid at its critical temperature. Water, for example, is a supercritical fluid when its temperature and pressure exceed 274.2 C. and 3204 psi (218.3 atm).
In recent years supercritical fluids have found use in a wide variety of applications. Supercritical fluids have been used for upgrading heavy crude oil and residual oils, for removing the mineral matter from liquified coal, and for dissolving and oxidizing hazardous organic chemical wastes. In use with olefins, supercritical water has exhibited potential to transform large olefins into other products. In U.S. Pat. No. 3,948,754, which relates to a process employing supercritical water and a catalyst for the recovery and upgrading of hydrocarbons from oil shale and tar sands, it was disclosed that supercritical water acting with an RuCl.sub.3 catalyst successfully yielded substantial quantities of octane from octene without the production of higher molecular weight species.